With the performance of LSI becoming more sophisticated, performance demand for insulating materials represented by buffer coat materials and rewiring layer materials for LSI chips is becoming more and more rigorous especially in the characteristics such as high resolution, low temperature cure, low stress and low dielectric constant. Specifically, in order to meet the demand for lower dielectric constants of interlayer insulating film materials, shear stress resistance and heat resistance are becoming weaker, higher speeds are demanded for rewiring layer materials, and, with an increased electric current density, the film of rewiring Cu is becoming thicker. Thus, it has become imperative that, in addition to the conventional high resolution, chemical resistance and temperature stress resistance, upper buffer coat materials and rewiring layers satisfy thick film-forming ability, planarizing ability, low stress, low dielectric constants, and low temperature-curing treatment.
Conventionally, as buffer coat materials and rewiring layer materials for LSI chips, photosensitive polyimides have been used as a representative example. The photosensitive polyimide may be formed by spin-coating a varnish containing a polyimide precursor having a double bond in the side chain and a photopolymerization initiator on an LSI wafer, and then only crosslinking the double bond on the side chain by a photo-crosslinking reaction, which may be developed to form a pattern, and subjected to a thermal curing treatment to decompose and volatilize the crosslinked chain and simultaneously to form a polyimide structure. Polyimides thus formed have excellent heat resistance, chemical resistance, and mechanical resistance.
As problems associated with such photosensitive polyimides, there can be mentioned that cracks may easily occur during thick film formation due to high residual stress, that planarizing ability on uneveness of the wafer top layer is low due to about 40% constriction that may occur during the thermal curing treatment, and that at low temperatures of less than 200° C. during the thermal curing treatment, the formation of a polyimide structure may be difficult and dielectric constant may not lower.
In contrast, Patent document 1 discloses a photosensitive silicone compound designated ORMOCER ONE of Fraunhofer ISC in Germany that may be obtained by the condensation of a trialkoxysilane having a photo-polymerizing functional group and a diarylsilanediol. Said compound may be easily patterned by lithographic exposure and development, and may be thermally cured at a temperature as low as 150° C. Furthermore, the cured product has a heat resistance of 300° C. or higher which is equal to that of polyimides, and simultaneously an excellent characteristics that cannot be attained with photosensitive polyimides as represented by a residual stress of 10 Mpa or less and a film loss of 3% or less between before and after thermal curing. However, it had problems (stickiness) that the stickiness of materials before exposure is great, that when touched to the mask during the exposure work, the materials may stick to the mask (stickiness), and the like.
Also, Patent document 2 discloses an inorganic/organic hybrid oligomer obtained by the condensation of a trialkoxysilane having a photo-polymerizing functional group and diphenylsilanediol using a tetraalkoxytitanium catalyst.    Patent document 1: Canadian patent Publication No. 2378756    Patent document 2: Japanese Unexamined Patent Publication (Kokai) No. 2005/298800